This invention relates to certain surfactant compositions comprising alkylxylene sulfonate compounds and to a method for displacing oil within a subterranean reservoir utilizing such compositions.
Compounds having valuable surface active properties are known to have been prepared from ortho-xylene by alkylation and then sulfonation. A mixture of several different isomers results, the predominant one of which is usually of the structure ##STR2## wherein R is an alkyl group, typically of about 6 to 20 carbon atoms, and M represent a hydrogen, a metal, an ammonium or an amine ion.
The alkyl ortho-xylene sulfonates have been recommended for use in various detergent compositions. In addition, because of their chemical and thermal stability, they are recognized as useful in various enhanced oil recovery techniques. Their application in oil recovery services is restricted to relatively low-salinity reservoirs, however, because the alkyl ortho-xylene sulfonates suffer from a limited solubility and salt-tolerance in water.
It is the principal object of the present invention to provide a novel surfactant composition characterized by favorable surfactant properties and stability, but one which is more soluble under high-salinity conditions.